In the production of automotive locks, the locks are commonly produced in sets of five, including two-door locks, an ignition lock, a trunk or deck lock, and a glovebox lock, and the locks are run in batches of twenty locks with the same coding. If any lock in the batch is shown to be defective, the entire batch is scrapped, as it is not economically feasible to repair the defective lock. For example, in order to repair a defective lock it would be necessary to remove the pawl and clip, the spring cap, the shutter unit and the shutter springs, and then remove the loaded cylinder from the case to change the tumblers. With high production rates as is required for automotive locks, it is not feasible to carry out this labor intensive process to repair the defective lock, with the result that the entire batch is scrapped.
U.S. Pat. No. 3,306,678 is directed to a pin tumbler lock having an opening in the case which is enclosed by a plastic cap. The pin tumblers extend into the opening in the case and a spring is interposed between the end of each pin and the cap. Due to the spring pressure against the cap, the cap is permanently secured to the case through a pinching or upsetting operation. The purpose of the cap in the aforementioned patent is to prevent entry of water into the pin tumbler chambers.